Modern innovations in cataract extraction, viz. new extracapsular techniques and the implantation of plastic intra-ocular lenses (pseudophakos), have increased the risk of phototoxic retinal damage from the illumination of the operating microscope. Clinically visible retinal lesions from such light toxicity have recently been noted in patients. Experimental studies in pseudophakic rhesus monkeys at our institution have shown that the threshold duration of exposure for production of a clinically visible retinal lesion when the eye is held in a fixed position is between 4.0 and 7.5 minutes with the microscope on the "high" illumination setting (ca. 0.49 w/cm2 in the human eye). This phototoxic retinal damage is caused primarily by the shorter wavelengths. The present study is designed to determine the efficacy of the commercially available Zeiss UV-430 filter in preventing such retinal damage. Rhesus monkeys will undergo extracapsular lens extraction and pseudophakos implantation in both eyes. One eye will be subjected to light exposure of a given duration with the UV-430 filter in place, whereas the second eye will undergo an equal duration of exposure with a neutral density filter that decreases overall illumination to the same extent as the UV-430 filter (ca. 12%). The degree to which the UV-430 filter protects the retina from the development of clinically visible lesions will thus be determined. Light and electron microscopy will be performed to study the lesions, comparing those produced with and without the UV-430 filter, and to determine whether there is histologic evidence of damage away from the clinically apparent lesion or in eyes receiving exposure durations below the threshold for production of a clinically apparent lesion.